In the removal of ion species or in the ion-exchange chromatography, ion species ionized to a high degree can be separated by the technique of ion-exchange resin and can be quantitatively analyzed by the use of an electroconductive cell, for example.
The first system of this kind was developed by Wickbold in Z. Anal. Chem., 132, 401 (1951). The initial apparatus so offered made use of no liquid pump and suffered from a disadvantage that the efficiency of the packed column was low and even the sensitivity was low. The ion chromatography subsequently developed by Small, Stevens, and Bauman (Anal. Chem., 47, 1801 (1975)) incorporated the principle of high-speed liquid chromatography and particularly materialized high-sensitivity analysis for various ions by the use of a deionization column. In this apparatus, since ions persist in large amounts in the deionization column as adsorbed on the ion exchanger, the deionization column must be subjected to a treatment for the regeneration of ion exchanger with the flow path thereof switched to some other flow path during the treatment. This apparatus, therefore, necessitates provision of a separate liquid pump. As the result, the apparatus has a disadvantage that the construction thereof gains in complexity and the consumption of acid or alkali regenerant is large. The method which uses ion-exchange membrane tubes in the place of the deionization column and effects analysis for anions by passing the eluate flow from the separation column through the afore-mentioned tubes, and causing cations in the eluate flow to depart outside from the ion-exchange membrane tubes through the membrane walls thereof by passing a reagent such as sulfuric acid or dodecylbenzenesulfonic acid through annular spaces formed between the outer wall surfaces of the ion-exchange membrane tubes and the inner wall surfaces of larger outer tubes disposed severally around the ion-exchange membrane tubes has been disclosed in Japanese Patent Application (OPI) Nos. 135156/81 and 57464/83, etc. (The term "OPI" as used herein means a "published unexamined Japanese patent application".) This method, however, is fated to the drawback that the reagent such as sulfuric acid or dodecylbenzenesulfonic acid by nature leaks inside into the ion-exchange membrane tubes through their membrane walls. This method, therefore, finds it improper to use this reagent in a high concentration. To cope with this trouble, this method inevitably necessitates means capable of regularly forwarding the reagent in a low concentration such as, for example, a pump and attendant piping and, at the same time, entails heavy consumption of acid for regeneration. An apparatus for working the method of this description becomes large and complicate.
Although various methods and apparatuses have been proposed to date for the analysis of aqueous solutions for component ions in minute amounts therein, none of them has proved satisfactory. The desirability of perfecting convenient and efficient method and apparatus for chromatographic analysis has been finding growing recoginition.
The inventors continued a diligent study for the purpose of making improvements capable of eliminating the numerous drawbacks mentioned above. They have consequently perfected a method for chromatographic analysis and an apparatus therefor which permit simultaneous, quick separation and detection of a plurality of component ions existing in minute amounts in an aqueous solution with high sensitivity and reproducibility over a protracted period of test.